Technical Field
The present invention relates to 1,3,4-oxadiazole and 1,3,4-thiadiazole compounds therapeutically useful as immune modulators. The invention also relates to pharmaceutical compositions comprising the said 1,3,4-oxadiazole and 1,3,4-thiadiazole compounds as therapeutic agents.
Description of the Related Art
Programmed cell death-1 (PD-1) is a member of the CD28 superfamily that delivers negative signals upon interaction with its two ligands, PD-L1 or PD-L2. PD-1 and its ligands are broadly expressed and exert a wider range of immunoregulatory roles in T cells activation and tolerance compared with other CD28 members. PD-1 and its ligands are involved in attenuating infectious immunity and tumor immunity, and facilitating chronic infection and tumor progression. The biological significance of PD-1 and its ligand suggests the therapeutic potential of manipulation of PD-1 pathway against various human diseases (Ariel Pedoeem et al., Curr Top Microbiol Immunol. (2011); 350:17-37).
T-cell activation and dysfunction relies on direct and modulated receptors. Based on their functional outcome, co-signaling molecules can be divided as co-stimulators and co-inhibitors, which positively and negatively control the priming, growth, differentiation and functional maturation of a T-cell response (Li Shi, et al., Journal of Hematology & Oncology 2013, 6:74).
Therapeutic antibodies that block the programmed cell death protein-1 (PD-1) immune checkpoint pathway prevent T-cell down regulation and promote immune responses against cancer. Several PD-1 pathway inhibitors have shown robust activity in various phases of clinical trials (R D Harvey, Clinical Pharmacology & Therapeutics (2014); 96 2, 214-223).
Programmed death-1 (PD-1) is a co-receptor that is expressed predominantly by T cells. The binding of PD-1 to its ligands, PD-L1 or PD-L2, is vital for the physiological regulation of the immune system. A major functional role of the PD-1 signaling pathway is the inhibition of self-reactive T cells, which serve to protect against autoimmune diseases. Elimination of the PD-1 pathway can therefore result in the breakdown of immune tolerance that can ultimately lead to the development of pathogenic autoimmunity. Conversely, tumor cells can at times co-opt the PD-1 pathway to escape from immunosurveillance mechanisms. Therefore, blockade of the PD-1 pathway has become an attractive target in cancer therapy. Current approaches include six agents that are either PD-1 and PD-L1 targeted neutralizing antibodies or fusion proteins. More than forty clinical trials are underway to better define the role of PD-1 blockade in variety of tumor types. (Hyun-Tak Jin et al., Clinical Immunology (Amsterdam, Netherlands) (2014), 153(1), 145-152).
International applications WO 01/14557, WO 02/079499, WO 2002/086083, WO 03/042402, WO 2004/004771, WO 2004/056875, WO2006121168, WO2008156712, WO2010077634, WO2011066389, WO2014055897, WO2014059173, WO2014100079 and U.S. patent U.S. Ser. No. 08/735,553 report PD-1 or PD-L1 inhibitory antibodies or fusion proteins.
Further, International applications, WO2011161699, WO2012/168944, WO2013144704 and WO2013132317 report peptides or peptidomimetic compounds which are capable of suppressing and/or inhibiting the programmed cell death 1 (PD1) signaling pathway.
Still there is a need for more potent, better and/or selective immune modulators of PD-1 pathway. The present invention provides 1,3,4-oxadiazole and 1,3,4-thiadiazole compounds which are capable of suppressing and/or inhibiting the programmed cell death 1 (PD1) signalling pathway.